1. Field of Invention
The present invention relates to a brake negative pressure generating device for a vehicle, and more particularly, to a brake negative pressure generating device which generates brake negative pressure by a supercharger when required.
2. Description of Related Art
In general, a vehicle draws external air therein, mixes the air with fuel, and supplies the mixture to an engine, and the engine gets the power required to drive the vehicle by combusting the mixture of air and fuel.
To achieve desired engine output and combustion efficiency, it is necessary to supply a sufficient amount of external air for combustion while generating power by driving the engine. Thus, a supercharger or turbocharger for pressurizing and supplying air for combustion has been adapted for use in vehicles in order to increase engine combustion efficiency and improve engine output.
The supercharger is configured to compress the air to be supplied to the engine by the pressure of the exhaust gas discharged from the engine.
However, there is a limit to compressing drawn air and supplying it to the engine only by the pressure of exhaust gas depending on the vehicle's traveling situation. As such, electrically-driven superchargers have been recently applied to vehicles to compress and supply drawn air by a compressor driven by an electric motor.
In the case of a vehicle using the aforementioned turbocharger or supercharger, if a brake pedal is operated after the engine goes into Wide Open Throttle (WOT) mode by stepping on the accelerator pedal as hard as possible, static pressure in the intake manifold cannot be properly released, though for a short period of time. This leads to a failure to generate sufficient negative pressure for brake force boosting, and hence the brake may be pulled back.
Moreover, when driving the vehicle on hilly roads, negative pressure generated in the intake manifold may not be sufficient for brake force boosting.
If the brake force boosting is not properly done because of insufficient negative pressure for brake force boosting, which is generated in the intake manifold and supplied to the brake system, this might be critical for the safe driving of the vehicle. Due to this, a vacuum pump for supplying sufficient brake negative power is installed in vehicles.
The vacuum pump installed to generate negative power for brake force boosting will increase the weight and cost of vehicles, and hence there is a need for a solution to overcome this problem.
The information disclosed in this Background section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.